<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>标签选择器</title>
  <style>
    div {
      color: brown;
    }
  </style>
</head>

<body>
  <!--  -->
  <div>
    我是一个div
    <div>
      我是子元素
      <div>我是孙子div</div>
    </div>
  </div>
</body>

</html>